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• byte-accurate ffmpeg segments

  12 février 2016, par Houseman

  Is there any way to use ffmpeg to accurately break audio files into smaller files of a specific file size, or pull a specific number of samples from a file?

  I'm working with a speech-to-text API that needs audio chunks in exactly 160,000 bytes, or 80,000 16-bit samples.

  I have a video stream, and I have an ffmpeg command to extract audio from it:

  ffmpeg -i "rtmp://MyFMSWorkspace/ingest/test/mp4:test_1000 live=1" -ar 16000 -f segment -segment_time 10 out%04d.wav
  

  So now I have ~10 second audio chunks with a sample rate of 16 kHz. Is there any way to break this into exactly 160kb, 5 second files using ffmpeg?

  I tried this:

  ffmpeg -t 00:00:05.00 -i out0000.wav outCropped.wav
  

  But the output was this:

  Input #0, wav, from 'out0000.wav':
    Metadata:
      encoder         : Lavf56.40.101
    Duration: 00:00:10.00, bitrate: 256 kb/s
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, 1 channels, s16, 256 kb/s
  Output #0, wav, to 'outCropped.wav':
    Metadata:
      ISFT            : Lavf56.40.101
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, mono, s16, 256 kb/s
      Metadata:
        encoder         : Lavc56.60.100 pcm_s16le
  Stream mapping:
    Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
  Press [q] to stop, [?] for help
  size=     156kB time=00:00:05.00 bitrate= 256.1kbits/s
  

  but now the size is 156kb

• How to get accurate time information from ffmpeg audio outputs ?

  11 février 2016, par user2192778

  I want to figure out the best way to have accurate (down to millisecond) time information encoded into a web stream audio recording. So, if I wanted to know what was streaming at exactly 07:57:25 yesterday, I could retrieve that information using my program code. How can I do this in my ffmpeg function?

  So far I have a python script that calls the following ffmpeg function every hour:

  ffmpeg -i http://webstreamurl.mp3 -t 01:30:00 outputname.mp3
  

  It will record 1.5 hours of my stream every hour. This leaves me with many 1.5 hour-long clips which together (due to some overlap) will give me audio at every moment.

  I don't know how I will sync these clips with their stream times, however. Is there a way to put timestamps in the audio and have python read it? Or is there a way to name these output files such that python could calculate the times itself? Any other way?

• c++ get supported camera resolutions and frame rate OSX

  11 février 2016, par Solidus

  I am using ffmpeg to record a video from a connected camera. I would like to be able to retrieve the supported camera resolution and framerate. Unfortunately this is currently not supported in ffmpeg on OSX. Are there other solutions out there? I've searched google and stackoverflow but the best I could find was a solution for windows using dshow.

  I imagine this is possible with avfoundation but I don't have any experience with it. I am also using qt (not quicktime, the qt framework) so it would have to be compatible with that. :)

  Thank you for your time.

• Unrecognized options even though compiled FFmpeg on Ubuntu manually

  11 février 2016, par Kathy Lee

  I would like to convert a video from .avi to .mp4 with same quality using ffmpeg but the command I put in the terminal always report some errors saying that there are unrecognized options.

  I have compiled the ffmpeg manually following the steps in http://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu

  After compiling the ffmpeg, I used the command below the compress the video

  ffmpeg -i input.avi -c:v libx264 -crf 19 -preset slow -c:a libfaac -b:a 192k -ac 2 output.mp4
  

  But the error message is saying "Unrecognized option 'crf'":

  ffmpeg version 2.8.5 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --enable-nonfree --enable-pic --enable-shared
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  Unrecognized option 'crf'.
  Error splitting the argument list: Option not found
  

  Then I tried to omit flag -crf, but I got error saying

  Unrecognized option 'preset'.
  Error splitting the argument list: Option not found
  

  Then I omitted flag -preset, it says I do not have libx264....

  [mjpeg @ 0x164f2c0] Changeing bps to 8
  Input #0, avi, from 'backup_bush.avi':
    Duration: 00:01:40.70, start: 0.000000, bitrate: 12409 kb/s
      Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj420p(pc, bt470bg/unknown/unknown), 400x250 [SAR 1:1 DAR 8:5], 12407 kb/s, 30 fps, 30 tbr, 30 tbn, 30 tbc
  Unknown encoder 'libx264'
  

  I am very confused what is going on because I have complied ffmpeg step by step and also installed the dependencies such as libx264 as described in http://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu. The command I used to configure ffmpeg is

   ./configure   --prefix="$HOME/ffmpeg_build"   --pkg-config-flags="--static"   --extra-cflags="-I$HOME/ffmpeg_build/include"   --extra-ldflags="-L$HOME/ffmpeg_build/lib"   --bindir="$HOME/bin"   --enable-gpl   --enable-libass   --enable-libfdk-aac   --enable-libfreetype   --enable-libmp3lame   --enable-libopus   --enable-libtheora   --enable-libvorbis   --enable-libvpx   --enable-libx264   --enable-nonfree
  

  Why these errors happen? How can I fix them to allow me to convert the video from .avi to .mp4?

  Thank you very much!

• Python matplotlib.animation [Errno 13] Permission denied

  11 février 2016, par Fishman

  I am trying to create a simple animated histogram and save it as a .mp4 using matplotlib and ffmpeg on a mac. I have already installed ffMpeg, specified the ffmpeg path, and now I am getting a permission denied error when writing to a folder in my desktop. I tried running as sudo and still get the same error. Help is much appreciated, thank you!

  Here is the code:

  df = pd.read_csv('.../data.csv')
  
  df = df.dropna()
  #Get list of weeks
  weeks = df.ot_date.unique()
  fig, ax = plt.subplots()
  
  data = df.intervals_filled[df['ot_date'].isin([weeks[0]])]
  n, bins = np.histogram( data , 20)
  
  # get the corners of the rectangles for the histogram
  left = np.array(bins[:-1])
  right = np.array(bins[1:])
  bottom = np.zeros(len(left))
  top = bottom + n
  nrects = len(left)
  
  # here comes the tricky part -- we have to set up the vertex and path
  # codes arrays using moveto, lineto and closepoly
  
  # for each rect: 1 for the MOVETO, 3 for the LINETO, 1 for the
  # CLOSEPOLY; the vert for the closepoly is ignored but we still need
  # it to keep the codes aligned with the vertices
  nverts = nrects*(1 + 3 + 1)
  verts = np.zeros((nverts, 2))
  codes = np.ones(nverts, int) * path.Path.LINETO
  codes[0::5] = path.Path.MOVETO
  codes[4::5] = path.Path.CLOSEPOLY
  verts[0::5, 0] = left
  verts[0::5, 1] = bottom
  verts[1::5, 0] = left
  verts[1::5, 1] = top
  verts[2::5, 0] = right
  verts[2::5, 1] = top
  verts[3::5, 0] = right
  verts[3::5, 1] = bottom
  
  barpath = path.Path(verts, codes)
  patch = patches.PathPatch(
      barpath, facecolor='green', edgecolor='yellow', alpha=0.5)
  ax.add_patch(patch)
  
  ax.set_xlim(left[0], right[-1])
  ax.set_ylim(bottom.min(), top.max()+40)
  ax.set_xlabel('Number of intervals/week')
  ax.set_ylabel('Count of CSAs')
  plt.rcParams['animation.ffmpeg_path'] = '/usr/local/Cellar/ffmpeg'
  FFwriter = animation.FFMpegWriter()
  
  def animate(i):
      print i
      # simulate new data coming in
      data = df.intervals_filled[df['ot_date'].isin([weeks[i-1]])]
      n, bins = np.histogram(data, 20)
      yearweek = str(weeks[i-1])
      year = yearweek[0:4]
      week = yearweek[4:]
      title = 'Week %(wk)s of %(yr)s' %{'wk': week, 'yr': year}
      ax.set_title(title)
      top = bottom + n
      verts[1::5, 1] = top
      verts[2::5, 1] = top
      return [patch, ]
  
  ani = animation.FuncAnimation(fig, animate, 53,interval=1000, repeat=False)
  ani.save('/Users/.../Desktop/1b.mp4', writer = FFwriter)
  plt.show()
  

  And here is the traceback:

  Traceback (most recent call last):
    File "/Users/Fishman1049/Desktop/reserves_histogram_timeline/python/1b_text.py", line 109, in 
      ani.save('/Users/Fishman1049/Desktop/1b', writer = FFwriter)
    File "/Users/Fishman1049/anaconda/lib/python2.7/site-packages/matplotlib/animation.py", line 761, in save
      with writer.saving(self._fig, filename, dpi):
    File "/Users/Fishman1049/anaconda/lib/python2.7/contextlib.py", line 17, in __enter__
      return self.gen.next()
    File "/Users/Fishman1049/anaconda/lib/python2.7/site-packages/matplotlib/animation.py", line 186, in saving
      self.setup(*args)
    File "/Users/Fishman1049/anaconda/lib/python2.7/site-packages/matplotlib/animation.py", line 176, in setup
      self._run()
    File "/Users/Fishman1049/anaconda/lib/python2.7/site-packages/matplotlib/animation.py", line 204, in _run
      creationflags=subprocess_creation_flags)
    File "/Users/Fishman1049/anaconda/lib/python2.7/subprocess.py", line 710, in __init__
      errread, errwrite)
    File "/Users/Fishman1049/anaconda/lib/python2.7/subprocess.py", line 1335, in _execute_child
      raise child_exception
  OSError: [Errno 13] Permission denied
  

  I am running matplotlib version 1.5.1, just installed FFmpeg today using homebrew, spyder 2.3.8, python 2.7 and OS X 10.10.5. Thank you!.